A carbonyl oxide route to antimalarial yingzhaosu A analogues: Synthesis and antimalarial activity

Ozonolysis of R-carvone and in situ trapping with primary alcohols ROH (R= Me, Et, Bu, Pent, Oct) produces hydroperoxy ketals (5a-e) as a 1:1 mixture of diastereomers. Cyclisation of these intermediates with catalytic sodium methoxide in methanol produces the corresponding endoperoxide derivatives (6a-6e). The pentyl and octyl endoperoxide derivatives demonstrate reasonable antimalarial potency in vitro against the HB3 strain of Plasmodium falciparum. A mechanism for antimalarial action involving the formation of a C-centred radical is proposed.